1. Field of the Invention
This invention pertains generally to the field of pressure regulators for breathing apparatus such as that used by underwater divers.
2. Description of the Prior Art
Pressure regulators are a necessary component of any underwater breathing apparatus, providing the necessary reduction of breathing gases from the high pressure of the tank to a lower pressure which is somewhat above ambient water pressure. In addition, the regulator must provide a means for controlling the flow of breathing mixture in accordance with the diver's demands. A first stage regulator at the tank is usually used to reduce the supply pressure to a substantially constant pressure above ambient, typically 130 to 150 psig. A second or final stage regulator receives the reduced pressure breathing mixture and meters it to the diver in accordance with his demands.
A common type of final stage pressure regulator employs a breathing chamber from which the diver draws breathing mixture and from which the diver's breath is exhausted. A flexible diaphragm is mounted across the breathing chamber and separates the gas in the chamber from ambient water. The diaphragm is drawn in as the diver inhales and is pushed out as the diver exhales. These movements of the diaphragm are transmitted by a lever to a valve connected to the source of breathing mixture such that inward movements of the diaphragm open the valve to allow breathing mixture to flow to the diver, whereas cessation of inhalation by the diver causes the diaphragm to move back out, thereby allowing a spring to close the valve and cut off the flow of breathing mixture to the diver. As the diver exhales, the contraction of his lungs increases the pressure in the breathing chamber and causes an exhalation port check valve to open to discharge the used breathing gases into the ambient water.
In regulators of the type just mentioned, substantial effort is required of the diver as he breathes to produce enough vacuum in the diaphragm chamber to force open the air supply valve on the intake stroke. In addition, the diver must force the gases from his lungs through the breathing chamber and the exhaust port, which requires a substantial effort on his part and contributes to diver fatigue.
Systems have been developed which provide some additional assistance during inhalation, for example by utilizing a pilot valve operated by the diaphragm which direct a portion of the breathing mixture to operate the main breathing supply valve. Such systems have a disadvantage in that they utilize the relatively high pressure breathing mixture input to control operation of the main valve, which renders the system potentially unstable, particularly at high breathing rates.